【摘要】 本文对一般形式的缺省理论进行了讨论，通过引入强相容缺省集概念，获得了缺省理论扩张存在的充分必要条件等重要结果．结果表明，缺省理论的扩张问题可以依据欧省集本身与初始公理作出判断，而不需要依赖于事先给定的闭公式集．最后，我们给出一实例，以示强相容集的构造方法．更多还原

【Abstract】 By introducing the concept of the strongly compatible subsets of defaults,the sufficient and necessary condition of the existence of extensions is gained. The result shows that the existence of extensions can be determined by the default set and the real world. An example shows how to construct the strongly compatible subsets of defaults.更多还原